Cord blood macrophages present bacterial antigen (Escherichia coli) to paternal T cells.

Cord-blood monocytes (cord-blood M phi s) pulsed with Escherichia coli or tetanus toxoid had the ability to present antigen and to induce proliferation of antigen-specific paternal T cells. The magnitude of the proliferative response was comparable (86 +/- 14%) to that obtained after co-culturing paternal T cells with antigen-pulsed autologous M phi s. Cord-blood M phi s were surface Ia positive (54 +/- 12% as compared to 78 +/- 6% of adult M phi s), which correlated well with their ability to present antigen, but the experimental design was not suitable to show quantitative relationships. Compared to M phi s from the peripheral blood of adults, cord-blood M phi s released equal or larger amounts of interleukin 1 upon stimulation with E. coli. Immunoadsorption studies showed the capacity of cord-blood M phi s to specifically remove E. coli-reactive T cells from a paternal T-cell pool (65% of antigen reactivity could be removed). This indicated that cord-blood M phi s were able to express bacterial antigen in their membrane. These results provide evidence that human mononuclear phagocytes are mature at birth with respect to surface Ia expression, release of interleukin 1, and presentation of bacterial antigen.